1. Field of the Invention
The present invention relates to a display apparatus capable of illuminating a light modulation device with a light from light emitting bodies such as a light emitting diode (hereinafter abbreviated as LED) to display an image on a display plane, a light source device for use in the display apparatus, and an illuminating unit which illuminates a region to be irradiated with the light from the light emitting body.
2. Description of the Related Art
Nowadays, an LED has won remarkable attention as a next-generation small-sized light emitting source. The LED has heretofore had advantages such as a small size, high resistance, and long life, but has mainly been used as indicator illumination for various measuring meters or a confirmation lamp in a control state because of restrictions on a light emitting efficiency and light emitting output. However, in recent years, the light emitting efficiency has rapidly been improved, and it is said to be a matter of time that the light emitting efficiency exceeds that of a high-pressure mercury lamp or a fluorescent lamp of a discharge type which has heretofore been assumed to have a high efficiency. Due to the appearance of the high-efficiency high-luminance LED, a high-output light emitting source using the LED has rapidly assumed a practicability. In recent years, a blue LED has been brought into a practical use stage in addition to conventional red and green LEDs, and this has also accelerated the application of the LED. In fact, a plurality of high-efficiency high-luminance LEDs have started to be practically used in a traffic signal lamp, large-sized full-color display for outdoors, various lamps for automobiles, and a backlight of a liquid crystal display of a cellular phone, although the practical use has heretofore been impossible in respect of brightness or efficiency.
The application of the high-efficiency high-luminance LED has been considered as a promising small-sized light emitting source of an illuminating unit which is requested to have a light condensing capability. The LED originally has characteristics superior to those of another light emitting source, such as life, durability, lighting speed, and lighting driving circuit. Furthermore, above all, blue is added, and three primary colors are all used in a self-light emitting source, and this has enlarged an application range of a full-color image display apparatus. Typical examples of the illuminating unit requested to have the light condensing capability include a projector display apparatus which forms and displays an image from image data. For the projector display apparatus, a desired primary color has heretofore been separated from a white system light emitting source via a color filter to subject the image data for each color to space light modulation, the data has been synthesized in space or time, and accordingly color image display has been possible. With the use of the white system light emitting source, since only one desired color is separated and used, colors other than the separated color are wasted/discarded by the filter in many cases. However, since the LED emits the light of a desired color, a necessary amount of light can be emitted when necessary. The light is not wasted, and the light of the light emitting source can efficiently be used as compared with a conventional white system light emitting source.
The superior application condition of the LED is noticed, and it is considered that the LED is also applied to the illuminating unit for the projector display apparatus as described in Jpn. Pat. Appln. KOKAI Publication No. 11-32278. In this case, a plurality of LEDs are arranged to bring the light for each LED in parallel with one another by a micro lens array. A light modulation device is illuminated by a reduced optical lens to constitute the projector device.
Moreover, as described in U.S. Pat. No. 6,227,669B1, a constitution has also been proposed for taking out output light from different LEDs (red (R) LED, green (G) LED, and blue (B) LED) by a light distribution lens array which is a light condensing optical system corresponding to each LED to superimpose the light from the plurality of LEDs upon the light modulation devices such as liquid crystal display by one superimposition lens.
Furthermore, as described in U.S. Pat. No. 6,318,863, a projector device is also proposed in which glass taper rods are disposed in the vicinity of the respective LEDs instead of the light distribution lens array to illuminate the light modulation device with the light from the rods by a superposition lens. This converts a luminous intensity distribution angle of the light emitted from the LED which is a plane light source and a diffused light source into a small luminous intensity distribution angle by the taper rods, and the efficiency of the illuminating of the light modulation device is improved.
Moreover, in recent years, as a display apparatus in a field of information display indoors or outdoors, a so-called full-color LED display system has rapidly started to spread in which the LED is used in each display body constituted of three color systems of red, green, and blue to constitute one pixel.
Various types of display apparatuses using the LED for each of red, blue, and green have been devised.
However, the LED has a large manufacturing fluctuation. Even when the same current is supplied to the LED, a constant brightness cannot be obtained in many cases. Therefore, in the display apparatus in which the LED is used, it is necessary to adjust a white balance at least at the time of the manufacturing.
As a method of solving the problems, the following methods have been proposed.
A display apparatus providing a high image quality has been proposed, for example, in U.S. Pat. No. 6,411,047 in which deviation to a basic color generated by the fluctuation in the manufacturing is corrected to eliminate color unevenness. This is a large-sized display apparatus constituted by integration of the pixels constituted by the three-color LEDs of red, green, and blue, a driving circuit for individually driving the LEDs of three colors of red, green, and blue is disposed in the device. Moreover, for example, when chromaticity of green that is a single light color deviates with respect to the chromaticity that is a standard of green, the LED of another color is allowed to emit the light, green is moved toward red or blue, and the chromaticity is adjusted so as to obtain an approximately standard chromaticity.
Moreover, a full-color display panel in which the LEDs of three primary colors of red, green, and blue are incorporated has a problem that the fluctuation of an emission intensity of each LED device is large and a uniform shade cannot be achieved. To solve the problem, in Jpn. Pat. Appln. KOKAI Publication No. 2001-343935, a panel has been proposed which is lit by a light driving circuit using an incorporated LED array. The emission intensity of the array is measured by a photoelectric conversion device, emission intensity to forward direction current characteristics specific to each LED device are obtained, and light driving is performed in accordance with a standard light intensity. Accordingly, it is possible to remove an individual difference fluctuation of the LED device, and a high-quality full-color display can be realized.
Furthermore, usual red, green, and blue system LEDs have a problem that each deterioration characteristic differs. As a display time elapses, that is, as an integrated display time increases, a reproduced color balance gradually collapses from an initial predetermined state, and a display color quality drops. To solve the problem, in Jpn. Pat. Appln. KOKAI Publication No. 2000-293133, a display apparatus has been proposed in which a full-color LED display system includes a monitor display portion to light white, the light emitted by the monitor portion is detected by an illuminance meter or a chromaticity meter, and the white balance and reproduced color balance can automatically be adjusted based on detected information.
Moreover, the examples of a method of correcting the white balance include the following disclosed examples. For example, in Jpn. Pat. Appln. KOKAI Publication No. 9-98443, a color correction device for use in color correction of data is disclosed in color image display apparatuses such as a full-color LED display panel and a color bulb display screen. This color correction device calculates hues of R, G, B data of an inputted CRT color image signal, and controls the lighting of the LEDs of R, G, B in consideration of a weighting factor in accordance with the hue.